1. Field of the Invention
The present invention relates to alkylborazine compound. Alkylborazine compound is used to form, for example, an interlayer dielectric film for semiconductor, a barrier metal layer and an etching stopper layer.
2. Description of Related Art
With higher functionalization of information devices, design rule of LSI has been required to be finer year by year. In production of LSI with finer design rule, materials composing LSI should also have higher performance and fulfill function even on fine LSI.
For example, as for materials used for an interlayer dielectric film in LSI, high dielectric constant causes signal delay. In fine LSI, effects of the signal delay is particularly significant. Therefore, development of a new low dielectric material which can be used for an interlayer dielectric film has been needed. Also to be used as an interlayer dielectric film, it is necessary not only to have low dielectric constant but also superior characteristics such as humidity resistance, heat resistance, mechanical strength, etc.
As a material to respond to these requirements, a compound having borazine ring backbone has been proposed (for example, see U.S. patent publication No. 2002-58142). A compound having borazine ring backbone has small molecular polarizability and thus a coated membrane formed provides low dielectric constant. Moreover, the coated membrane formed is superior in heat resistance.
As a borazine-ring containing compound, various compounds have been proposed up to now. For example, alkylborazine compound, whose boron moiety is substituted with alkyl group, has very superior characteristics as a low dielectric material (for example, see JP-2003-119289A). Alkylborazine compound, whose boron moiety is substituted with alkyl group, can be synthesized by preparing B,B′,B″-trichloro-N,N′,N″-trialkylborazine such as B,B′,B″-trichloro-N,N′,N″-triethylborazine as a raw material, and by substituting a chlorine atom of the compound with alkyl group by using a Grignard reagent (for example, see D. T. HAWORTH and L. F. HOHNSTEDT, J. Am. Chem. Soc., 82, 3860 (1960)).
Alkylborazine compound synthesized is purified in response to usage after synthesis. As purification methods, sublimation purification, wherein a mixture is separated utilizing difference in sublimation temperature specific to a compound, and distillation purification, wherein a mixture is separated utilizing difference in boiling temperature specific to a compound are known.